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Published on: January 26, 2011
Cloning and sequencing of the gene encoding variant-specific surface antigen from Giardia lamblia
Ya-Jie Li1, Mei-Jun Teng, Yong-Zhi Lun
1Department of Pathogenic Biology, Medical College of Dalian University, Dalian 116622, China. Liyj@dlu.edu.cn
Objective:
To clone and sequence variant-specific surface antigen gene from Giardia lamblia isolate SUCH/89/BTMR/2(C2) derived from human in China.
Methods:
Total genomic DNA of G. lamblia was extracted and a full-length variant-specific surface antigen gene fragment was amplified by polymerase chain reaction (PCR). The PCR product was cloned into pMD19-T simple-vector, transformed into an Escherichia coli JM109 strain and then sequenced. The sequence analysis for cloned fragment was finished by Vector NTI 9.0 software for the homology of Giardia variant-specific surface antigen gene to that of sequences published in GenBank.
Results:
The full-length variant-specific surface antigen gene fragment from G. lamblia was found to be 2 142 bp, encoding a 713 amino acid polypeptide and contained a single open reading frame (ORF). The deduced polypeptide sequence was rich in cysteine (11.8 mol%), most of which occurred with in 29 copies of the 4-amino acid CXXC motif, one GGCY-tetrapeptide motifs and three NXS consensus N-linked glycosylation sites. This polypeptide was also rich in threonine (10.2 mol%), glycine (12.1 mol%) and alanine (10.1 mol%). Like other previously identified VSPs, it contained a highly conserved hydrophobic C-terminal region. The homology of G. lamblia SUCH/89/BTMRI/2(C2) variant-specific surface antigen gene to that of sequence (TSA417) published in GenBank was 99% both at the nucleotide and the amino acid levels.
Conclusion:
The full length variant-specific surface antigen gene from the isolate of G. lamblia has the common characteristics with other previously identified VSPs.
